Artist's rendition of a wildlife corridor over a highway in the Sonoran Desert

When habitat gets fragmented, or broken up, it can be difficult for species to get from one place to another- like coyotes attempting to get from one forest patch to another through a bunch of houses! In conservation, we often look to what we call corridors for a solution to habitat fragmentation. Corridors are like hallways of habitat connecting one patch to another, making it easier for a coyote, or a beetle, to get from one patch of forest to the next. While we conservationists usually think of corridors as important in semi-natural areas (through agricultural or forestry fields or highways), they can actually be used in an urban context! And for insects!

Fig. 1 from Vergnes et al. Map of the Paris region showing urban sites (A) and schema of the sampling design (B) of a site. (A). Open and rural land cover are presented in white. Woodlands are represented in black. Urban cover is represented in grey. Sites are indicated by white circles (s01 to s04). (B) A site is composed of 4 green space types: a source (S), a corridor (C), 4 connected gardens (CG) and 4 disconnected gardens (DG).

Vergnes et al.studied the different types of ground beetles, rove beetles, and spiders in private home gardens in the Greater Paris area. They compared the numbers and types of these beetles and spiders in gardens connected to a tree lined corridor and those not connected to the corridor (see Fig. 1). The corridor was full of oak trees and connected back to a park, also a woodland. They found that the same types of beetles and spiders that were in the park were also in the gardens connected to the park via the corridor; this was particularly true for beetles that have a harder time dispersing from the park to the surrounding gardens without a corridor. Insects can be poor at dispersing for many reasons but usually because they can’t fly or because they are habitat specialists. Some beetles that can’t disperse well weren’t found in the disconnected gardens at all- like the rove beetle below.

The Rove Beetle Plataraea brunnea- a poor disperser found only in the woodland, corridors, and connected gardens. Photo from http://www.koleopterologie.de

While the researchers found many species of spiders and rove beetles, they were surprised by how few ground beetles (family of tiger beetles!) they found- even in the park! Thinking at a larger scale, they realized that the ground beetles might not even be able to disperse to the urban park in the first place!

This paper is neat because it shows that urban corridors are important to maintaining biodiversity and that corridors are needed at both large scales, from the rural areas inward, and at small scales, from urban parks to home gardens.